Since the Skyhawk was mentioned, as well as the subject of ice and wind, it
may be that ice loading and the lack of a truss system will lead to
catastrophic failure of the Skyhawk boom.
I have pictures of neighbor's (AC9S) Skyhawk in 2006
(http://www.csm-gh.com/ac9s-skyhawk-5.htm) after it broke. Shorter boom
beams and those with truss systems in the area survived the ice and wind.
Given the possibility of ice storms in this location, were I to buy a
Skyhawk, I'd also create a truss system for it for added survivability. The
Skyhawk is a great antenna when its all in one piece in the air. The TH-7
may not be as good as the Skyhawk, but my TH-7 didn't break and it stayed in
one piece in the air (using the BN-4000 as the balun).
73 & DX,
Gary - AB9M
-----Original Message-----
From: Kelly Taylor
Sent: Thursday, February 26, 2015 1:29 PM
To: Jim Thomson ; towertalk@contesting.com
Subject: Re: [TowerTalk] Mosley Antenna Question
Other examples of trapless multi-band antennas include the DX Engineering
Skyhawk, designed by K3LR, the new line of N6BT antennas (the DX4r, etc.) as
well as the multiband antennas from JK Antennas (such as the JK tribander (2
el on 15 and 20 and 4el on 10)).
All benefit from reduced surface area (no traps), optimal element spacing
(all have band-specific placement for all parasitic elements) and no trap
losses.
And, even if some of these antennas give up a little bit in gain, it's more
than made up for with, in some cases, reduced tower and rotator
requirements.
None of this is to bash anything or anyone. If you have a TH7 or a Pro57b,
it has probably served you well and will probably continue to serve you
well. What has changed, however, is that for someone shopping new, today,
technology and computer modelling have given us much more to think about
than traps and size.
It's also been fairly well established down through the ages that an
optimized 2 el. monoband yagi equals or betters a three-element tribander,
owing to the compromised element spacing and trap losses of the tribander.
Put three of these optimized 2 el. yagis on one boom, and optimize for
element interaction, and you have a tribander, optimized for all three
bands.
Those who are still clinging to 1960s methodologies would do themselves a
favour and open their eyes and look around.
73, kelly
ve4xt
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